1. Field of the Invention
The invention relates to an apparatus and method for cleaning wafers with contact holes or via holes; in particular, the invention relates to a wafer-cleaning apparatus and method that disposes the wafer in a manner such that its surface, with contact holes or via holes, faces downward during cleaning.
2. Description of the Related Art
In ultra large scale integration (ULSI) process, for example, before wafers enter a high-temperature chamber or after being subjected to thin-film etching, the wafers must be subjected to chemical cleaning, de-ionized (DI) water rinsing and drying so the surface of the wafer can attain the requirement of high cleanliness. Wafer-cleaning technique affects the yield, the quality of the device and the reliability. Wafer cleaning removes contamination on the surface of the wafer, such as particles, organic and metal ions.
The wafer-cleaning technique comprises a wet chemical cleaning and a physical cleaning technology. No matter which procedure is used, a step in which DI water sprays or cleans the wafer is included.
In FIG. 1, a conventional wafer-cleaning apparatus, using DI water, is shown. Such apparatus comprises a vacuum chuck 22, a rotary shaft 24 and a sprayer 26. The vacuum chuck 22 fixes a wafer 10 by vacuum. The rotary shaft 24, disposed beneath the vacuum chuck 22 and connected with the vacuum chuck 22, rotates the vacuum chuck 22. The rotary shaft 24 rotates at high speed so that the wafer 10, disposed on the vacuum chuck 22, rotates at high speed. The sprayer 26, disposed above the vacuum chuck 22, sprays DI water downwards to the surface of the wafer 10, as shown by arrow A and arrow B.
In FIG. 2, a cross-section of the wafer 10 with via holes is shown. The wafer 10 is provided with a substrate 12, a metal layer 14 and a dielectric layer 16. The dielectric layer 16, for example, is oxide material. The via hole 30, defined by etching, is located inside the dielectric layer 16. When the wafer 10, as shown in FIG. 2, is disposed in a manner such that a surface S, with the via hole 30, of the wafer 10 faces upward, as shown in FIG. 1, the spraying DI water remains in the via hole 30 due to gravity. As a result, native oxide 40 is formed inside the via hole 30 so as to affect the characteristic of the device. In addition, because of gravity and the angle of the spraying water, defects, generated on the surface of the wafer, are splashed up by the water, easily fall back onto the surface of the wafer. Thus, the problem of defects remaining on the surface of the wafer often occurs.
In order to address the disadvantages of the aforementioned wafer-cleaning technique, the invention provides an apparatus and method for cleaning wafers with contact holes or via holes that can reduce the possibility of native oxide remaining in contact or via holes.
Another purpose of the invention is to provide an apparatus and method for cleaning wafers with contact holes or via holes that can enhance the removal of defects from the surface of the wafer.
Accordingly, the invention provides an apparatus for cleaning wafers with contact holes or via holes comprising a first arm, a second arm, a fixing device, a rotating device and a spraying device. The fixing device, disposed on the first arm, fixes the wafer in a manner such that a surface of the wafer, with contact holes or via holes, faces downward. The rotating device, disposed above the fixing device, rotates the fixing device. The spraying device, disposed on the second arm in a manner such that the spraying device is located beneath the fixing device, sprays the water upwards to the surface of the wafer.
Furthermore, the fixing device is a vacuum chuck, and the spraying device is a sprayer.
The spraying device comprises a nozzle. The apparatus further comprises an oscillator and a controller. The oscillator, disposed on the second arm, communicates with the nozzle. The controller electrically connects to the oscillator.
The invention provides a method for cleaning wafers with contact holes or via holes comprising the following steps. First, a substrate is provided, and at least one dielectric layer is formed on a surface of the substrate. Then, the dielectric layer is etched to form the contact holes or via holes, and the substrate is disposed in a manner such that its surface, with contact holes or via holes, faces downward. Finally, the water is applied upwards to the surface of the substrate.
Furthermore, the water is de-ionized water.